/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.dx.dex.code;

import com.android.dx.rop.code.RegisterSpecList;
import com.android.dx.rop.code.SourcePosition;

/**
 * Instruction which has a single branch target.
 */
public final class TargetInsn extends FixedSizeInsn {

	/** {@code non-null;} the branch target */
	private CodeAddress target;

	/**
	 * Constructs an instance. The output address of this instance is initially
	 * unknown ({@code -1}), and the target is initially {@code null}.
	 * 
	 * @param opcode
	 *            the opcode; one of the constants from {@link Dops}
	 * @param position
	 *            {@code non-null;} source position
	 * @param registers
	 *            {@code non-null;} register list, including a result register
	 *            if appropriate (that is, registers may be either ins or outs)
	 * @param target
	 *            {@code non-null;} the branch target
	 */
	public TargetInsn(Dop opcode, SourcePosition position,
			RegisterSpecList registers, CodeAddress target) {
		super(opcode, position, registers);

		if (target == null) {
			throw new NullPointerException("target == null");
		}

		this.target = target;
	}

	/** {@inheritDoc} */
	@Override
	public DalvInsn withOpcode(Dop opcode) {
		return new TargetInsn(opcode, getPosition(), getRegisters(), target);
	}

	/** {@inheritDoc} */
	@Override
	public DalvInsn withRegisters(RegisterSpecList registers) {
		return new TargetInsn(getOpcode(), getPosition(), registers, target);
	}

	/**
	 * Returns an instance that is just like this one, except that its opcode
	 * has the opposite sense (as a test; e.g. a {@code lt} test becomes a
	 * {@code ge}), and its branch target is replaced by the one given, and all
	 * set-once values associated with the class (such as its address) are
	 * reset.
	 * 
	 * @param target
	 *            {@code non-null;} the new branch target
	 * @return {@code non-null;} an appropriately-constructed instance
	 */
	public TargetInsn withNewTargetAndReversed(CodeAddress target) {
		Dop opcode = getOpcode().getOppositeTest();

		return new TargetInsn(opcode, getPosition(), getRegisters(), target);
	}

	/**
	 * Gets the unique branch target of this instruction.
	 * 
	 * @return {@code non-null;} the branch target
	 */
	public CodeAddress getTarget() {
		return target;
	}

	/**
	 * Gets the target address of this instruction. This is only valid to call
	 * if the target instruction has been assigned an address, and it is merely
	 * a convenient shorthand for {@code getTarget().getAddress()}.
	 * 
	 * @return {@code >= 0;} the target address
	 */
	public int getTargetAddress() {
		return target.getAddress();
	}

	/**
	 * Gets the branch offset of this instruction. This is only valid to call if
	 * both this and the target instruction each has been assigned an address,
	 * and it is merely a convenient shorthand for
	 * {@code getTargetAddress() - getAddress()}.
	 * 
	 * @return the branch offset
	 */
	public int getTargetOffset() {
		return target.getAddress() - getAddress();
	}

	/**
	 * Returns whether the target offset is known.
	 * 
	 * @return {@code true} if the target offset is known or {@code false} if
	 *         not
	 */
	public boolean hasTargetOffset() {
		return hasAddress() && target.hasAddress();
	}

	/** {@inheritDoc} */
	@Override
	protected String argString() {
		if (target == null) {
			return "????";
		}

		return target.identifierString();
	}
}
